1. Technical Field
The present invention relates to transmission line interfaces in general and, in particular, to transmission line interfaces for interconnecting integrated circuits. Still more particularly, the present invention relates to a selectable interface for interfacing integrated circuit modules.
2. Description of the Prior Art
The operating frequencies of integrated circuits have increased to the point that interconnection between circuit modules require techniques that are more sophisticated than impedance matching and pulse shaping. Typically, driver/receiver circuits use transmission lines that must span distances approaching a fraction of a wavelength at the processing frequencies since the shape of logic pulses is dependent on higher harmonics of the processing frequencies. Either single-ended interfaces or differential interfaces can be found in such driver/receiver circuits.
Both single-ended interfaces and differential interfaces have their advantages or disadvantages. For example, a differential interface requires two connections, which effectively reduces data throughput per wire. However, compared to single-ended interfaces, differential interfaces are usually less susceptible to common-mode noise and can provide a symmetrical load on power supplies and ground returns. Differential interfaces also have relatively better noise immunity because information that causes a state change in a signal line provides a corresponding opposite change in a complementary signal line. In addition, a differential interface is desirable for interconnects that are associated with the hot-insert capable interconnect, as a connector and cables or longer circuit board interconnects are needed to provide the hot insertion capability.
In light of the above, the present disclosure provides an improved interface for interfacing integrated circuit modules.
In accordance with a preferred embodiment of the present invention, a bus interface for interconnecting a first circuit module and a second circuit module includes a transmitter pair located within the first circuit module and a receiver pair located within the second circuit module. The transmitter pair, which can be selectable between a differential mode and a single-ended mode, transmits data from the first circuit module to the second circuit module. The receiver pair, which can also be selectable between a differential mode and a single-ended mode, receives data from the transmitter pair.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.